Nonvolatile memory devices are an important element of electronic systems due to their ability to maintain data absent a power supply. Some nonvolatile memory cells include phase change materials. Phase change materials include chalcogenide compounds, which are capable of stably transitioning between physical states (e.g., amorphous, semi-amorphous, and crystalline states). Each physical state may exhibit a particular resistance that may be used to distinguish a logic value of the memory cell.
Conventional memory cells including the phase change materials may also include a selector device (such as, for example, a switching diode, a threshold switching material, another isolation element, etc.). One type of selector device material may include a chalcogenide compound, such as one exhibiting an OFF state that is relatively resistive and an ON state that is relatively conductive. The ON state may be enabled when a voltage across the selector device material is greater than a critical value of the selector device material.
Fabrication of conventional semiconductor structures including such memory cells often includes creating high aspect ratio openings in a stack of materials comprising the memory cells to form stack structures on a substrate. Frequently, materials that are highly sensitive to downstream processing conditions are used as part of the stack structures. For example, chalcogenide materials of the phase change material, the selector device material, or both, may be damaged at temperatures used during conventional semiconductor fabrication processes or may react with etchant or deposition chemistries used during downstream processing. The chalcogenide materials may also diffuse out of the chalcogenide material during etching or material formation (e.g., deposition) acts. In some situations, the chalcogenide material may undesirably have a different composition after fabrication of the semiconductor structure than an as-deposited chalcogenide material.
To overcome such problems, liners have been formed over sidewalls of the stack structures including the reactive chalcogenide materials. However, deposition of a liner material increases fabrication time and cost. In addition, deposition of such liner materials may negatively affect the thermal budget and alter a composition of the chalcogenide materials by, for example, diffusion. Further, chalcogenide materials of the phase change material, the selector device material, or both, may react with deposition chemistries or etch chemistries used during respective deposition or etching of the liner materials. Further, as-deposited liner materials may delaminate from surfaces of the chalcogenide and the stack structures and may not, therefore, effectively passivate the chalcogenide materials.